A power transmission shaft used in automobiles and various industrial machines is generally made of steel. However, the power transmission shaft made of steel is heavy. Therefore, in recent years, in order to reduce the weight, fiber reinforced plastic, such as carbon fiber reinforced plastic (CFRP), is used in some cases.
When the fiber reinforced plastic is used as described above, an iron and steel member is used together in order to prevent decrease in strength. Therefore, it is necessary to join the fiber reinforced plastic and the iron and steel member to each other, and a joining property between the fiber reinforced plastic and the iron and steel member has hitherto been taken into consideration (Patent Literatures 1 to 3).
In Patent Literature 1, a tube body made of fiber reinforced plastic (FRP) is joined to a metallic yoke in an end portion of the tube body through intermediation of a rivet. In this case, the tube body made of FRP is formed of a right angle winding layer in which fibers are wound so that an orientation angle thereof is substantially a right angle with respect to a center axis. In the end portion, an acute angle winding layer in which fibers are wound so that an orientation angle thereof is an acute angle with respect to the center axis and the right angle winding layer are alternately arranged.
In Patent Literature 2, an end portion of a tubular body made of FRP includes a helical winding layer in which an orientation angle of fibers is set to less than 45° with respect to a center axis and a hoop winding layer interposed in the helical winding layer. The orientation angle of fibers of the hoop winding layer is set to 45° or more and less than 90°. An intermediate cylindrical member formed of a metal plate is press-fitted into the end portion, and further, a press-fitting shaft portion of a metallic yoke is fitted into the intermediate cylindrical member.
In this case, serrations are formed on a radially outer surface and a radially inner surface of the intermediate cylindrical member. When the intermediate cylindrical member is press-fitted into the end portion of the tubular body made of FPR, the serration on the radially outer surface side cuts into the radially inner surface of the end portion of the tubular body made of FRP. Further, when the press-fitting shaft portion of the metallic yoke is fitted into the intermediate cylindrical member, the serration formed on the radially outer surface of the press-fitting shaft portion of the metallic yoke is meshed with the serration on the radially inner surface. With this, the metallic yoke is joined to the tubular body made of FRP.
In Patent Literature 3, there is disclosed a FRP drive shaft in which metallic end portion joints are coupled to both end portions of an FRP cylinder. In this case, the end portion joint includes a serration shaft member and a large-diameter flange member coupled to the serration shaft member. A metallic butt collar formed of a short cylindrical body including a corrugated engagement portion is externally fitted onto the serration shaft member, and the end portion of the FRP cylinder is fitted into the serration shaft member in an outer fitting shape.
Further, a corrugated engagement portion is formed in the end portion of the FRP cylinder, and the corrugated engagement portions are fitted with each other under a state in which the corrugated engagement portion of the butt collar is brought into abutment against the corrugated engagement portion formed in the end portion of the FRP cylinder. Then, the collar formed of the short cylindrical body is externally fitted onto the fitting site of the corrugated engagement portion. In this case, the corrugated engagement portion of the FRP cylinder and the corrugated engagement portion of the collar are fitted with each other, and in this state, the collar is externally fitted to adhere onto the fitting site of the corrugated engagement portion. The FRP cylinder and the butt collar, which are integrated, are press-fitted into the serration shaft member.